This invention relates generally to the use and structure of removable nonvolatile memory devices, particularly those having standardized connectors for interfacing with other electronic systems.
Electronic circuit cards, including non-volatile memory cards, have been commercially implemented according to a number of well-known standards. Memory cards are used with personal computers, cellular telephones, personal digital assistants (PDAs), digital still cameras, digital movie cameras, portable audio players and other host electronic devices for the storage of large amounts of data. Such cards usually contain a re-programmable non-volatile semiconductor memory cell array along with a controller that controls operation of the memory cell array and interfaces with a host to which the card is connected. Several of the same type of card may be interchanged in a host card slot designed to accept that type of card. However, the development of the many electronic card standards has created different types of cards that are incompatible with each other in various degrees. A card made according to one standard is usually not useable with a host designed to operate with a card of another standard. Memory card standards include PC Card, CompactFlash™ card (CF™ card), SmartMedia™ card, MultiMediaCard (MMC™), Secure Digital (SD) card, a miniSD™ card, Subscriber Identity Module (SIM), Memory Stick™, Memory Stick Duo card and TransFlash™ memory module standards.
Small, hand-held re-programmable non-volatile memories have also been made to interface with a computer or other type of host through a Universal Serial Bus (USB) connector. These are especially convenient for users who have one or more USB connectors available on the front of their personal computers, particularly if a receptacle slot for one of the above identified memory cards is not present. Such devices are also very useful for transferring data between various host systems that have USB receptacles, including portable devices. Mechanical and electrical details of the USB interface are provided by the “Universal Serial Bus Specification,” revision 2.0, dated Apr. 27, 2000. USB connectors generally feature a metal shell surrounding an opening that contains pins, the metal shell connecting to ground when inserted into a USB receptacle. There are several USB flash drive products commercially available from SanDisk Corporation under its trademark “Cruzer®.” USB flash drives are typically larger and shaped differently than the memory cards described above.
Removable memory units (cards, USB flash drives and other units) are generally provided with a standardized connector. In some cases, such connectors are susceptible to damage. A cap may be used to cover such a connector so that it is protected. However, where such covers are separable from the memory unit, they may be lost or damaged easily. One alternative is to provide a connector that retracts into the housing of the memory unit for protection. Examples of such units include Cruzer® Titanium USB flash drives from SanDisk Corporation. In order to provide physical protection, the housing of a flash drive may be made of a metal, such as steel, stainless steel, aluminum, titanium, zinc, a suitable alloy or any other suitable metal.
A unit with a retractable connector generally has a feature on the outside of its housing that allows a user to manually slide the connector between a retracted position and an extended position. In the retracted position, the connector is contained within the housing and is protected by the housing. In the extended position, the connector extends through an opening in the housing so that it may be plugged into a receptacle. Such an opening is generally made somewhat larger than the connector so that there is some clearance around the connector to allow it to freely extend and retract without significant friction or binding.
Under normal circumstances, some electrostatic charge can develop on the conductive housing which may lead to Electrostatic Discharge (ESD) issues. ESD is a discharge of transient charge that may develop on a conductive housing or on a body that is in electrical contact with the housing, causing the housing to be at higher electrical potential with respect to ground requiring a ground path to discharge. Hence many electrical/electronic systems are furnished with ESD protection circuits. These circuits prevent an unwanted transient charge that may develop on a conductive housing from jumping onto sensitive components within the memory system and hence prevent the damage or failure of memory devices. One way to design for ESD protection is to provide a ground path to chassis (PC) ground via a metal shell of a connector.
A conductive spring provided between the connector and the housing provides an electrically conductive pathway between the housing and the metal shell of the connector. Thus, the housing and the metal shell are kept at the same potential. When the connector is connected to a receptacle, the metal shell is connected to ground and any charge on the housing is discharged through the conductive spring to the conductive shell. In this way, the memory system is protected from damaging electrostatic discharge. In one example, the conductive spring is formed integrally with the metal shell of the connector.
Additional aspects, advantages, features and details of various aspects of the present invention are included in the following description of exemplary embodiments thereof, which description should be taken in conjunction with the accompanying drawings.
All patents, patent applications, articles, manuals, standards, specifications, other publications and things referenced herein are hereby incorporated herein by those references in their entirety for all purposes.